Hi Xiaolan! On Monday 07 Dec 2009 12:20:45 Xiao Lan (小兰) wrote: > Hello, > > > I have a text whose content is like: > > aabbbbaa > bbaaaabbaa > aaxxxbb > bb776yhghhaa > > > I want to switch all "aa" and "bb". > I can handle this use regex: > > s/aa|bb/$& eq 'aa'?'bb':'aa'/ge; > > > But how to use 'tr' doing that? >
The short answer is that you cannot. The tr/// operator operates only on characters. so tr/ab/ba/ will also change "ac" to "bc" and "ab" to "ba", etc. I once contemplated writing something called strtr to convert entire strings into different ones, but then thought it would be too much trouble for too little gain and that s/// can do all that and more. Your s/// solution is OK, though you should: 1. Avoid using $& because it makes things slower globally. See the warning on perldoc perlvar: http://perldoc.perl.org/perlvar.html Instead, do: s/(aa|bb)/$1 eq 'aa' ? 'bb' : 'aa'/ge; 2. You may opt to use a hash for more complicated substitutions. Regards, Shlomi Fish > Thanks. > > //Xiao lan > -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ "Humanity" - Parody of Modern Life - http://shlom.in/humanity Bzr is slower than Subversion in combination with Sourceforge. ( By: http://dazjorz.com/ ) -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
